Tanker aircraft are used to perform aerial or in-flight refueling, which is the process of transferring aviation fuel from one aircraft, namely the tanker aircraft, to another aircraft during flight. Air refueling increases the endurance of the aircraft receiving fuel from the tanker aircraft, which may extend the range of the aircraft. It is also possible to perform a series of air refuelings, which can further extend the range of the receiving aircraft. Another advantage of air refueling is that it allows the receiving aircraft to take off with a greater payload and a lesser fuel supply, which can be topped off with fuel from a tanker aircraft once the receiving aircraft is airborne and at a cruising altitude.
Tanker aircraft typically include extra fuel tanks located in the aircraft body and in or on the aircraft wings. The fuel tanks both fuel the tanker aircraft propulsion systems, such as jet engines, and contain fuel to be off loaded to the receiving aircraft. Efforts have been made to increase the fuel carrying capacity of tanker aircraft. In one such effort, twin rigid fuel tanks are mounted on a pallet that is rolled into and secured within the cargo area of the tanker aircraft. The tanks are connected to a common conduit that is connected to a fuel port within the cargo area that is connected to fuel tanks integral to the aircraft.
These rigid tanks require a mechanical pump to pump fuel from the tanks through the common conduit and into the fuel port within the cargo area. The tanks can be controlled by the pilot of the tanker aircraft. When the tanks are emptied, they can be rolled off of the tanker aircraft out of the cargo area and refilled.
Although such auxiliary tanks increase the fuel carrying capacity of a tanker aircraft significantly, the design is relatively expensive because it requires additional pumps, and the flow of fuel from the two tanks must be balanced to maintain a consistent center of gravity of the auxiliary tanks within the cargo area. Accordingly, there is a need for an auxiliary or extension fuel system for a tanker and/or cargo aircraft that is relatively low cost, provides a greater capacity for additional fuel than current methods and systems, streamlines integration with existing derivative aircraft systems, and may not require venting as is required of such rigid auxiliary fuel tanks.